1. Field of the Invention
The present invention relates generally to a key structure, and more particularly, to a key structure applicable in an electronic device such as a notebook computer.
2. Description of Related Art
Due to the requirement for portability, a conventional notebook computer is often equipped with a device for controlling a screen cursor. Early on, a conventional notebook computer is equipped with a track ball that functions as the device for controlling the screen cursor. Touch pads and trackpoints are commonly found in the present market. Trackpoints are mainly applied in notebook computers manufactured by the International Business Machines (IBM) Co. In practice, to facilitate manipulation of a touch pad or a trackpoint, keys, which are equivalent to the left and right keys of a mouse, are usually installed in front of the keyboard, and electrical buttons intended to generate electrical signals are installed under the keys.
U.S. Pat. No. 6,177,924 B1 disclosed a key fixing structure for fixing a key installed inside the base of a notebook computer to the bottom surface of the upper housing of the notebook computer. A pair of through holes is installed on the upper housing of the notebook computer, and a key set including two keys protrudes out of the surface of the upper housing via the respective through holes. The keys are provided with elastic arms and thereby return to the original height when pressed and released.
FIG. 1 shows another known key structure for touch pads used in notebook computers. A key structure 1′ having a big plastic frame is embedded in an upper housing 2 of a notebook computer. A touch pad 2′ is embraced in the key structure 1′. The key structure 1′ comprises a pair of keys 11′ and annulus sections 12′ for connecting the keys 11′. The annulus sections 12′ engage with the upper housing 2 of the notebook computer, so as to enable the keys 11′ to form cantilever structures and return to the original height when pressed and released.
However, the above known designs share a common drawback, that is, a key will overtravel if pressed too hard. If this happens all the time, the elastic arm or the annulus section is likely to loss its elasticity, and in consequence the key does not return to the original height but becomes sunken. In addition, appearing in the form of a cantilever structure and being roughly aligned with the surface of the upper housing of the notebook computer, the key moves aside and protrudes upward if the user has a bad habit of pulling a button.
Furthermore, a certain gap exists between the upper housing of the notebook computer and a key of the key fixing structure disclosed in both U.S. Pat. No. 6,177,924 B1 and FIG. 1, and therefore dust or liquid, such as water, may enter the notebook computer through the gap, thus damaging inner components of the notebook computer.
Accordingly, an issue that currently needs urgent solution involves developing a key fixing structure intended for the touch pad of a notebook computer, to overcome various drawbacks of the aforesaid conventional technology, preventing the keys from becoming sunken or protruding upwards, and avoiding intrusion of foreign bodies and the resultant damage which may otherwise be done to inner components.